A combustion chamber of an engine includes a cylinder block, a piston and a cylinder head. The temperature of the metal surface of the combustion chamber is controlled at a temperature of about 200° C. so that engine oil can be used. For this purpose, the respective parts need to be cooled. For example, the cylinder block and the cylinder head can be cooled using an engine coolant and the piston can be cooled by spraying oil onto a lower part of the piston.
When cooling of the combustion chamber is not favorable, the temperature of the combustion chamber is increased, abnormal combustion occurs and thus engine hunting occurs. In addition, oil temperature may increase, lubrication function may deteriorate and oil consumption may increase.
Accordingly, in order to reinforce cooling of the combustion chamber, research has been conducted on coating the surfaces of cast iron liners used for cylinder blocks with an aluminum material having a high thermal conductivity.
When a bore of the cylinder block constitutes a combustion chamber and allows the piston to reciprocate, an upper part of the combustion chamber should be cooled well, whereas middle and lower parts of the combustion chamber in which the piston reciprocates need to maintain the temperature well so as to maintain viscosity.
Meanwhile, as the temperature of the cylinder increases, the cylinder bore thermally expands. As a result, the temperature of the cylinder may be changed between positions according to direction of the axis line of the cylinder. Accordingly, variation of the cylinder bore is also changed according to the axis line direction due to thermal expansion. The difference in variation of the cylinder bore may cause an increase in friction of the piston and deteriorating fuel consumption.
In an attempt to solve the above mentioned problems in the related arts, the present invention may provide a cylinder liner for insert casting which may have cooling and warming properties suitable for functions of respective parts of the bore and a method for manufacturing the same.